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AC'97 (short for Audio Codec '97; also MC'97, short for Modem Codec '97) is Intel Corporation
Intel Corporation

Intel Corporation is the world's largest semiconductor company and the inventor of the X86 architecture series of microprocessors, the processors found in most personal computers....
's Audio "Codec
Codec

A codec is a device or computer program capable of encoder and/or Decoding methods a digital data stream or signal . The word codec is a portmanteau of 'compressor-decompressor' or, most commonly, 'coder-decoder'....
" standard developed by the Intel Architecture Labs
Intel Architecture Labs

Intel Architecture Labs, also known as IAL, was the Personal Computer system research and development arm of Intel Corporation during the 1990s....
 in 1997, and used mainly in motherboard
Motherboard

A motherboard is the central printed circuit board in some complex electronic systems, such as modern personal computers. The motherboard is sometimes alternatively known as the mainboard, system board, or, on Apple Inc....
s, modem
Modem

Modem is a peripheral device that modulation an analog carrier wave Signal to encode digital information, and also demodulation such a carrier signal to decode the transmitted information....
s, and sound card
Sound card

A sound card is a computer expansion card that facilitates the input and output of sound to/from a computer under control of computer programs....
s.

Intel's use of the word audio codec
Audio codec

An audio codec is a hardware device or a computer program that data compression digital audio data according to a given audio file format or streaming media....
 refers to signals being encoded/decoded to/from analog audio from/to digital audio
Digital audio

Digital audio uses digital signals for sound reproduction. This includes Analog-to-digital converter, Digital-to-analog converter, storage, and transmission....
, thus actually a combined audio AD/DA
Digital-to-analog converter

In electronics, a digital-to-analog converter is a device for converting a digital code to an analog signal .An analog-to-digital converter performs the reverse operation....
-converter. This should not be confused with a codec in the sense of converting from one binary format to another, such as an audio (MP3
MP3

MPEG-1 Audio Layer 3, more commonly referred to as MP3, is a digital audio Encoder format using a form of lossy data compression. It is a common audio format for consumer audio storage, as well as a de facto standard encoding for the transfer and playback of music on digital audio players....
) or video (Xvid
XviD

Xvid is a video codec library following the MPEG-4 standard, specifically MPEG-4 Part 2. It uses ASP features such as b-frames, global and quarter pixel motion compensation, lumi masking, trellis quantization, and H.263, MPEG and custom quantization ....
) codec in a media player.

Audio components integrated into chipset
Chipset

A chipset or chip set refers to a group of integrated circuits, or chips, that are designed to work together. They are usually marketed as a single product....
s consists of two components: an AC'97 digital controller (DC97), which is built into the I/O Controller Hub
Southbridge (computing)

The Southbridge, also known as an Input/output Controller Hub or a Platform Controller Hub in Intel systems , is a chip that implements the "slower" capabilities of the motherboard in a northbridge/southbridge chipset computer architecture....
 (ICH) of the chipset, and an AC'97 audio and modem codecs, which is the analog component of the architecture.






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AC'97 (short for Audio Codec '97; also MC'97, short for Modem Codec '97) is Intel Corporation
Intel Corporation

Intel Corporation is the world's largest semiconductor company and the inventor of the X86 architecture series of microprocessors, the processors found in most personal computers....
's Audio "Codec
Codec

A codec is a device or computer program capable of encoder and/or Decoding methods a digital data stream or signal . The word codec is a portmanteau of 'compressor-decompressor' or, most commonly, 'coder-decoder'....
" standard developed by the Intel Architecture Labs
Intel Architecture Labs

Intel Architecture Labs, also known as IAL, was the Personal Computer system research and development arm of Intel Corporation during the 1990s....
 in 1997, and used mainly in motherboard
Motherboard

A motherboard is the central printed circuit board in some complex electronic systems, such as modern personal computers. The motherboard is sometimes alternatively known as the mainboard, system board, or, on Apple Inc....
s, modem
Modem

Modem is a peripheral device that modulation an analog carrier wave Signal to encode digital information, and also demodulation such a carrier signal to decode the transmitted information....
s, and sound card
Sound card

A sound card is a computer expansion card that facilitates the input and output of sound to/from a computer under control of computer programs....
s.

Intel's use of the word audio codec
Audio codec

An audio codec is a hardware device or a computer program that data compression digital audio data according to a given audio file format or streaming media....
 refers to signals being encoded/decoded to/from analog audio from/to digital audio
Digital audio

Digital audio uses digital signals for sound reproduction. This includes Analog-to-digital converter, Digital-to-analog converter, storage, and transmission....
, thus actually a combined audio AD/DA
Digital-to-analog converter

In electronics, a digital-to-analog converter is a device for converting a digital code to an analog signal .An analog-to-digital converter performs the reverse operation....
-converter. This should not be confused with a codec in the sense of converting from one binary format to another, such as an audio (MP3
MP3

MPEG-1 Audio Layer 3, more commonly referred to as MP3, is a digital audio Encoder format using a form of lossy data compression. It is a common audio format for consumer audio storage, as well as a de facto standard encoding for the transfer and playback of music on digital audio players....
) or video (Xvid
XviD

Xvid is a video codec library following the MPEG-4 standard, specifically MPEG-4 Part 2. It uses ASP features such as b-frames, global and quarter pixel motion compensation, lumi masking, trellis quantization, and H.263, MPEG and custom quantization ....
) codec in a media player.

Audio components integrated into chipset
Chipset

A chipset or chip set refers to a group of integrated circuits, or chips, that are designed to work together. They are usually marketed as a single product....
s consists of two components: an AC'97 digital controller (DC97), which is built into the I/O Controller Hub
Southbridge (computing)

The Southbridge, also known as an Input/output Controller Hub or a Platform Controller Hub in Intel systems , is a chip that implements the "slower" capabilities of the motherboard in a northbridge/southbridge chipset computer architecture....
 (ICH) of the chipset, and an AC'97 audio and modem codecs, which is the analog component of the architecture. AC'97 defines a high-quality, 16- or 20-bit
Bit

A bit is a binary numeral system numerical digit, taking a value of either 0 or 1. Binary digits are a basic unit of information Computer data storage and transmission in digital computing and digital information theory....
 audio architecture with surround sound
Surround sound

Surround sound, using multichannel audio, encompasses a range of techniques for enriching the Sound recording and reproduction quality, of an audio source, with additional audio channels reproduced via additional, discrete speakers....
 support for the PC that is used in the majority of today's desktop platforms. AC'97 supports 96,000 samples/second in 20-bit stereo resolution and 48,000 samples/second in 20-bit stereo for multichannel recording and playback.

Integrated audio is implemented with the AC'97 Codec on the motherboard
Motherboard

A motherboard is the central printed circuit board in some complex electronic systems, such as modern personal computers. The motherboard is sometimes alternatively known as the mainboard, system board, or, on Apple Inc....
, a Communications and Networking Riser
Communications and Networking Riser

Communications and Networking Riser, or CNR, is a Edge connector found on certain PC motherboards and used for specialized networking, audio, and telephony equipment....
 (CNR) card, or an audio/modem riser
Audio/modem riser

The audio/modem riser, also known as an AMR slot, is an expansion slot found on the motherboards of some Pentium III, Pentium 4, and Athlon personal computers....
 (AMR) card.

AC '97 v2.3 enables Plug and Play audio for the end user. This version provides parametric data about the analog device
Analog device

Analog device is an machine that measures continuous information. The measured analog signal has an infinite number of possible Value s. The only limitation on Angular resolution is the accuracy of the measuring device....
 being used.

In 2004 AC'97 was superseded by Intel High Definition Audio
Intel High Definition Audio

Intel High Definition Audio refers to the specification released by Intel in 2004 for delivering high-definition sound reproduction that is capable of playing back more channels at higher quality than previous integrated audio codecs like AC97....
 (HD Audio).

AC-Link


The AC-Link is a digital link that connects the DC97 (the controller) with the audio "codecs." It is composed of 5 wires: the clock (12.288 MHz), a sync signal, a reset signal, and two data wires, namely sdata_out (contains the DC97 output) and sdata_in (contains the codec output). The AC-Link provides a bidirectional (one using sdata_out and the other using sdata_in), fixed bitrate (12.288 Mbit/s), serial digital stream between one controller and several audio codecs.

Each 12.288 Mbit/s stream is divided into 256-bit frames (frame frequency is 48 kHz). This is therefore a time division multiplexing (TDM
Time-division multiplexing

Time-Division Multiplexing is a type of digital or Pulse-amplitude modulation multiplexing in which two or more signals or bit streams are transferred apparently simultaneously as sub-channels in one communication channel, but are physically taking turns on the channel....
) scheme.

Every frame is subdivided in 13 slots, from which slot 0 (16 bits) is used to specify which audio codec is talking to the controller. The remaining 240 bits are divided in 12 20-bit slots (slots 1-12), used as data slots.

Each data slot (48 kHz, 20 bits/sample) is used to transmit a raw PCM audio signal (960 kbit/s). Several data slots in the same frame can be combined into a single high-quality signal (maximum is 4 slots, obtaining a 192 kHz, 20 bit/sample, stereo signal).

Since AC-Link is a fixed-frequency link, all sample rate conversion
Sample rate conversion

Sample rate conversion is the process of converting a signal from one sampling rate to another, while changing the information carried by the signal as little as possible....
 should be performed in the DC97 (controller) or in the software driver.

Problems

  • Audio Settings:
The AC97 is shipped for Microsoft operating systems (Windows XP
Windows XP

Windows XP is a line of operating systems produced by Microsoft for use on personal computers, including home and business desktops, laptop, and media centers....
 and Vista
Windows Vista

Windows Vista is one member in a family of operating systems developed by Microsoft for use on personal computers, including home and business Desktop computer, laptops, Tablet PCs, and media center PCs....
) with an audio settings program. Various versions of this program exist, for configuring the audio settings including the input and output connector configuration, sound effects, an equalizer
Equalization

Equalization, equalisation or EQ is the process of using passive or active electronic elements or digital algorithms for the purpose of altering the frequency response characteristics of a system....
 "mixer board", 3D sound configuration, and microphone echo cancellation
Echo cancellation

The term echo cancellation is used in telephony to describe the process of removing echo from a voice communication in order to improve voice quality on a telephone call....
. Many people are not aware of this program, and once pointed to this program, find that an unwanted sound effect was inadvertently set to be active.

  • AC97 Soundcard Connector Configuration Problem:
Most of the AC97 on-board sound card versions are typically shipped with three RCU connectors marked in three colors: pink, green and blue, according to PC99 Color-coding scheme
PC System Design Guide

The PC System Design Guide is a series of hardware design requirements and recommendations for IBM PC compatible personal computers, compiled by Microsoft and Intel Corporation during 1997?2001....
. The pink connector is meant for a microphone, the green either for line-out to amplified speakers, or to a line-in wire, and the blue has an amplified signal for un-amplified or slightly amplified headphones. The audio settings program has a problem when set to Headphones or to Stereo Speakers, and will only work when configured to be set as a multi-speaker unit with 3 speakers or more. The speakers actually attached to one of the outputs (and only one output typically works), are behaving as background speakers for 3D sound effect, and for this reason will play only music and not talking, or will work only with a sound effect set on, and no sound will be heard when the sound effect is set to NONE. In many cases no solution has been found for this problem, and most technical advice sites advise to simply buy a low-cost external soundcard.

  • Microsoft Update Acknowledged AC97 Soundcard Problem:
Microsoft has acknowledged that in one of their automatic updates they have caused the AC97 to stop working. This has been corrected in a subsequent version of updates, and is now treated as missing the updated driver.

Codec chips

Codec chips have an AC97 interface on one side and analog audio interface on the other. They are usually small square chips with 48 pins. They are D/A and A/D or only D/A.

  • Analog Devices
    Analog Devices

    Analog Devices is an United States Multinational corporation producer of semiconductor devices. Analog specializes in analog-to-digital converter, digital-to-analog converter, MEMS, and digital signal processing chips for consumer and industrial goods....
     AD1819B, 1881A, 1885, 1886, 1887, 1980, 1981, 1985
  • AKM (Asahi Kasei Microsystems) AK 4540, 4543, 4544A, 4545
  • Avance Logic (now Realtek
    Realtek

    Realtek Semiconductor Corp. , a Fabless semiconductor company situated in the Hsinchu Science Park, Hsinchu, Taiwan, was founded in October 1987, and subsequently approved as a listed company on the Taiwan Stock Exchange in 1998....
    ) ALC201A, ALC202/A, ALC650, ALC655, ALC658, ALC101, ALC202A, ALC250, ALC850
  • Conexant
    Conexant

    Conexant Systems Inc. is a publicly listed United States semiconductor company, which was formerly the semiconductor division of Rockwell International....
     Cx20468 - with a modem
  • Cirrus Logic
    Cirrus Logic

    Cirrus Logic is a fabless semiconductor company specializing in analog, mixed-signal, and audio DSP integrated circuits . They are presently headquartered in Austin, Texas....
     CrystalWare 4236, CrystalClear SoundFusion CS4297, CS4299
  • Crystal Semiconductors CS4205, CS4202
  • C-Media
    C-Media

    C-Media Electronics, Inc. is a Taiwanese computer hardware company that manufactures processors for PC audio and USB storage, and wireless audio devices....
     CMI9738, 9739, 9761, 9880
  • ESS ES1988 (with a modem)
  • Empia EMP202 (2 channel, 20-bit DAC and 20-bit ADC, full duplex AC'97 2.2 compatible stereo audio CODEC)
  • Intersil
    Intersil

    Intersil Corporation specializes in the design and manufacture of high-performance analog semiconductors for four high-growth markets ? Communications, Computing, High End Consumer and Industrial....
     HMP9701 (obsolete, 48 kHz fixed samplerate)
  • National Semiconductor
    National Semiconductor

    National Semiconductor is a semiconductor manufacturer, specializing in analog devices and subsystems,headquartered in Santa Clara, California, California, United States....
     LM 4540, 43, 45, 46, 48, 49, 50
  • Philips
    Philips

    Koninklijke Philips Electronics N.V. , usually known as Philips, is a Netherlands electronics company. It is one of the largest electronics companies in the world, founded and headquartered in the Netherlands....
     UCB 1400 (with touchscreen controller)
  • Realtek
    Realtek

    Realtek Semiconductor Corp. , a Fabless semiconductor company situated in the Hsinchu Science Park, Hsinchu, Taiwan, was founded in October 1987, and subsequently approved as a listed company on the Taiwan Stock Exchange in 1998....
     ALC658, ALC655, ALC650, ALC268
  • SigmaTel
    SigmaTel

    SigmaTel is an electronics company located in Austin, TX, which designs mixed Audio signal processing, and microcontroller for multifunction peripherals....
     (now IDT
    Integrated Device Technology

    IDT was founded in 1980 as a semiconductor vendor. Employing approximately 2500 people worldwide, headquartered in San Jose, California, and operating a Fab in Hillsboro, Oregon, the company both designs and fabricates semiconductor components....
    ) C-Major STAC 9460 (D/A only), 9461, 9462, 9463, 9200, 9202, 9250, 9251, 9220, 9221, 9223, 9750
  • Silicon Image Si3024 (mono only)
  • TriTech Microelectronics TR28022, 28026
  • Yamaha YMF 743, 752, 753
  • VIA
    VIA Technologies

    VIA Technologies is a Taiwanese manufacturer of integrated circuits, mainly motherboard chipsets, Central processing unit, and computer memory, and is part of the Formosa Plastics Group....
     VT1612, VT1616 (VIA Six-TRAC Vinyl Audio), VT82C686
  • Winbond
    Winbond

    Winbond Electronics Corporationis a Taiwan-based corporation which was founded in 1987 and is a producer of semiconductors and several types of Integrated Circuit, most notably DRAM, Static Random Access Memory, microcontrollers, and personal computer integrated circuit....
     W83971
  • Wolfson Microelectronics
    Wolfson Microelectronics

    Wolfson Microelectronics is a Scotland microelectronics and fabless semiconductor corporation specialising in signal processing microchip for the consumer electronics market....
     WM9701, WM9703, WM9704, WM9705 (w/touchscreen), WM9707, WM9708, WM9709 (DAC only), WM9711, WM9712 (w/touchscreen), WM9713 (w/touchscreen), WM9714


External links

  • Intel Corporation, February 2005, Version 1.3


See also

  • I²S
    I²S

    I2S, or Inter-IC Sound, or Integrated Interchip Sound, is an electrical serial bus interface standard used for connecting digital audio devices together....
     (Integrated Interchip Sound)
  • Audio/modem riser
    Audio/modem riser

    The audio/modem riser, also known as an AMR slot, is an expansion slot found on the motherboards of some Pentium III, Pentium 4, and Athlon personal computers....
     (AMR)
  • Advanced Communications Riser
    Advanced Communications Riser

    The Advanced Communications Riser, or ACR, is a form factor and technical specification for PC motherboard expansion slots. It is meant as a supplement to Peripheral_Component_Interconnect slots, a replacement for Audio/modem_riser slots, and a competitor and alternative to Communications and Networking Riser slots....
     (ACR)
  • Communications and Networking Riser
    Communications and Networking Riser

    Communications and Networking Riser, or CNR, is a Edge connector found on certain PC motherboards and used for specialized networking, audio, and telephony equipment....
     (CNR)
  • S/PDIF
    S/PDIF

    File:TOS LINK clear cable.jpgS/PDIF specifies a OSI model#Layer_2:_Data_Link_layer protocol and choice of OSI model#Layer_1:_Physical_layer specifications for carrying digital audio Signalling s between Peripheral devices and Hifi#Modularity....
     Sony/Philips Digital Interface Format